With the rapid explosion in the use of cellular telephone communications systems in the United States, it is not uncommon to find vehicles equipped with a cellular telephone communication system. Such vehicle mounted cellular telephone communication systems are not only used for voice communication between the driver of the vehicle and a remote monitoring system but are also used to provide data describing the location of the vehicle, data concerning events occurring at the vehicle and data describing the condition of the vehicle--to the remote monitoring station. Such data may include the latitude and longitude of the vehicle, the condition or state of any of the numerous operating systems which are resident on a motor vehicle, and the occurrence of an event such as theft of the vehicle, a vehicle fire, an accident or an alarm condition, such as a medical emergency, sensed by the driver.
When a cellular telephone communication system is used to provide the location of the vehicle such location is normally provided by using the signals transmitted by one or more orbiting satellites. Such orbiting satellites are part of the Global Positioning System (GPS). The signals received by the vehicle from the orbiting GPS satellites are translated by a tracking module mounted in the vehicle. The tracking module converts signals received from one or more orbiting GPS satellites into latitude and longitude data. In addition to the transmission of location data, there is also a critical need to assure that voice communication between an operator at the remote monitoring station and the occupants of the vehicle is not overly hampered by the transmission of data.
Therefore, the design criteria for a cellular communication system between a vehicle and a remote monitoring station should include:
Easily understandable voice conversation with minimal interruption by the transmission of data;
Assurance of data integrity; PA1 Determination of loss of the communication link; PA1 User-friendly, reliable operation; PA1 Ability to function in high noise environments having multiple communication link impairments; PA1 Recognition of repeated commands in either direction.